1. Field
The disclosed embodiments generally relate to techniques for converting DC power to different voltages. More specifically, the disclosed embodiments relate to a technique for actively controlling power loss in a switched-capacitor power converter.
2. Related Art
A high-efficiency switched-capacitor power converter is comprised of one or more switched-capacitor blocks (SCBs), which are driven by a resonant clocking circuit to generate an output voltage VHI which is nearly double an input voltage VLO. To operate at the highest possible efficiency, a switched-capacitor power converter needs to minimize power losses during the voltage-conversion process. These power losses include both (1) conduction losses in the SCBs and (2) switching losses in the SCBs and resonant clocking circuit.
Fortunately, these losses can be controlled by varying a gate drive voltage VG generated by the resonant clocking circuit to drive switching transistors in the SCBs. More specifically, increasing VG increases switching losses and at the same time decreases conduction losses. Conversely, decreasing VG increases conduction losses and decreases switching losses. Hence, VG can be adjusted to achieve a balance between switching losses and conduction losses that minimizes power loss in the power converter.
Unfortunately, the relative magnitudes of the conduction losses and switching losses vary as the operating point of the power converter changes over time. More specifically, the relative magnitudes of the conduction losses and switching losses can vary with changes in the root-mean-square output current IRMS and the input voltage VLO. As a consequence, the value of VG that minimizes power loss varies as the operating point of the power converter changes.
Hence, what is needed is a method and an apparatus for controlling power loss in a switched-capacitor power converter in a manner that accounts for changes in the operating point of the power converter.